There are authors who don't cotton to hand-holding, and then there are authors who drop you off in the middle of Times Square on New Year's Eve, distract you with a party favor, and then run the other way as fast as they can. Maybe you'll eventually find your way in the throng, even if you are tear-streaked and sniffling by the time you do (did I mention you are 5?). Maybe at the end of it you've learned something (most likely that there are a bunch of people in Times Square who desperately want you to attend a comedy show) and are a little stronger for it. Or your mind has snapped and you have been reduced to a blubbering, shell-shocked simpleton. Fifty-fifty.Hannu Rajaniemi is, clearly, the latter type, and I'm still not quite sure what my trek through this book has done to me. Not since Neuromancer has a sci-fi book left me questioning how a bunch of words could be strung together in logical, well-crafted sentences and still not make any sense. Both books made me feel dumb and slow and a bad reader. I don't think this is my fault, but I also doubt it was the writers' intention.See, they both create richly imagined new worlds out of reassembled bits and pieces of what we recognize as reality, mixing things up with new gadgets and technology and the repercussions of fictional disasters. And they just plop us down into these worlds and never, ever tell us what is going on. I totally get avoiding exposition dumps and telling versus showing, but seriously, this book hurt my brain. There are concepts -- key plot concepts -- that the characters take as rote parts of their everyday lives that are introduced on page 1 and not clearly explained until maybe 75 percent of the way through the book. The primary antagonists are roughly sketched at best, and even though all the characters know who they are and what they're about, we don't get anything but hints up until the epilogue. But it's not just that -- technology is referenced again and again before we get an idea of what it does. For about half the book, I wasn't sure if it was happening inside of a computer or not. See what I mean about feeling dumb?But it's ok for a few reasons. One, Hannu Rajaniemi lays down some of the sharpest prose I've encountered in genre writing, dense without feeling mannered, spare and yet evocative. This is a short novel by space opera standards, and he shows those bloated quasi-epics how it's done. (Of course, snipping out all that exposition is a good way to start.) Two, the plot is a fairly straightforward Whodunnit mixed with elements of One Last Job, with a thief and a detective squaring off, sprinkled with a Mysterious Backstory and some small-r romance. When books make me work this hard, I don't mind if I can see some of the structure poking through. It's nice to have a clue if it's going to be able to support my weight.Three, the SFnal ideas here are pretty great. Novel twists on familiar concepts (including a nifty take on the "uploading consciousness into the cloud" trope) are just the start; there's also this wonderful riff on our growing concern for privacy through the invention of a system that allows you to control what you share with people all the time. You can walk down the street cloaked in privacy, so anyone passing won't recognize you unless you want them to. You can even edit what parts of a conversation someone will be able to remember (which removes a lot of the potential awkwardness from one-night stands). Lots of sci-fi has explored they way memory shapes reality, but Rajaniemi manages to find a fresh angle.So, should you read this? I'd say it depends on A) your comfort level with having no idea what the hell is happening for hundreds of pages, and B) your familiarity with the genre. Because while not the trickiest book I've ever read, this is hardly elementary school SF. That's what you get when you let Finnish mathematical physicists write books.